save fields

add_action( 'save_post', '_save_postdata' );
function _save_postdata( $post_id ) { 
	if ( 'location' == $_POST['post_type'] ) {
		if ( ! current_user_can( 'edit_page', $post_id ) )
			return;
	} else {
		return;
}

		
	if ( ! isset( $_POST['_noncename_contact'] ) || ! wp_verify_nonce( $_POST['_noncename_contact'], plugin_basename( __FILE__ ) ) ) {
		//return;
	}

	$meta_keys = array( 
		//meta keys
	);
	
	if ( substr( $_POST['_google_map_tld'], 0, 1) == "." ) 
		$_POST['_google_map_tld'] = substr( $_POST['_google_map_tld'], 1 );
	
	//sanitize checkbox fields
	$checkbox_array = array(		
		//checkbox meta keys
	);
	
	foreach ( $checkbox_array as $checkbox ) {
		if ( empty( $_POST[$checkbox] ) ) 
			$_POST[$checkbox] = 'off';
	}


	foreach ( $meta_keys as $meta_key ) {
		$meta_key = NS_PREFIX . '_' . $meta_key;
		$old_meta_data = get_post_meta( $post_id, $meta_key, true ); 
		$new_meta_data = sanitize_text_field( $_POST[$meta_key] );
		if ( $new_meta_data && $new_meta_data != $old_meta_data ) {  
			update_post_meta( $post_id, $meta_key, $new_meta_data );  
		} elseif ( '' == $new_meta_data && $old_meta_data) {  
			delete_post_meta( $post_id, $meta_key, $old_meta_data );  
		}
	}	
}